1. Field of the Invention
The present invention relates to an exhaust system for use with a v-configured internal combustion engine having a close-mounted catalytic converter as an aid to early converter light-off and, more particularly, to an exhaust system having a pre-chamber adjacent to the converter which acts to prevent reversion of particles into the engine.
2. Description of the Relevant Art
Typical automotive exhaust systems incorporate catalytic converters which operate to reduce the level of harmful emissions generated by the vehicle's internal combustion engine. A standard practice is to locate the converter in an under-floor configuration in a manner similar to most vehicle mufflers. The under-floor location is convenient from a space utilization aspect, however, the remote mounting encourages heat loss from the exhaust gas during its transit from the engine to the converter. Such heat loss affects the efficiency of the converter in that it increases the time to light-off, which is the temperature the converter must reach before it begins to effectively reduce exhaust emissions.
One method of reducing converter light-off time is to "close-couple" the converter to the engine. In effect, the converter is placed as close as possible to the exhaust ports of the engine, thereby reducing the distance the gas must travel after leaving the engine and minimizing the heat loss therefrom. On v-configured engines, this method generally requires the use of one catalytic converter mounted adjacent each exhaust bank with the outlets joined further downstream of the engine. This configuration is inefficient from the standpoint of cost and complexity since it requires the use of an additional converter which represents a substantial cost penalty. Additionally, the close proximity of the converters to the exhaust ports of the engine require special precautions to be taken, especially in the case of ceramic converter monoliths, to prevent particles generated by the converter from being drawn into the engine.